A water-containing polymer gel has a structure similar to that of a living body, and has a property of expanding or shrinking depending on external conditions such as temperature, acidity, and alkalinity. Accordingly, applications in the medical field, including a use as an artificial organ or tissue such as an artificial muscle or encapsulation of a drug therein to control an amount to be released, have been attempted, as well as applications as an anchorage of cell growth in a cell culture as a gel containing various kinds of cytokines and the like.
It is known that cells are arrayed with polarity when they form a tissue in a living body. For example, hepatocytes absorb blood components from the vascular endothelial cell side, and excrete metabolites such as bile acid from the opposite side. Since this bile acid has potent cytotoxicity, cell culture by adhering the cells on an ordinary petri dish for cell culture suffers from a problem that stable long-term culture is difficult. Although it is also known that the polarity of cells is expressed by stimulation given from one way to the cells, cell culture by adhering the cells on an ordinary petri dish for cell culture causes a problem that stimulation cannot be given from the adhesion side.
To solve these problems, a permeable collagen membrane for cell culture, MEN-01, is sold by KOKEN CO., LTD. as a cell culture material for culturing cells with different media for the both sides of the cells. However, in this product, the collagen membrane is much swelled with a medium, and thus the product is significantly distorted during the culture. Therefore, it is difficult to observe a culture state of cells. Further, a carrier for cell culture is proposed which comprises a porous membrane together with an alginic acid gel layer and an extracellular matrix component gel layer or an extracellular matrix component sponge layer, which are laminated on the porous membrane (Japanese Patent Unexamined Publication (KOKAI) No. 2001-120267). However, this carrier for cell culture has a microfilter layer, and therefore, growth state of cells cannot be observed under an optical microscope. Furthermore, a polymer complex of chitosan and an anionic cellulose derivative is proposed as a carrier for cell culture (Japanese Patent Unexamined Publication (KOKAI) No. 6-277038). However, chitosan and the anionic cellulose derivative will form a gel immediately after mixing, and therefore it is difficult to obtain a carrier for cell culture having a flat and smooth surface.
As further problems, since such a gel swells after immersion in a medium to lose strength, it is difficult to take out a cell culture out of the medium. In addition, since the gel cannot be attached only to a minute space, the gel was also unsuitable for construction of cell chips in which cells are divided into minute spaces and cultured.